A windshield wiper blade conventionally comprises a mounting member consisting of at least one stirrup which is adapted to hold a wiping strip, which is generally made of rubber based material. It has been found that, in operation and when the vehicle in which the wiper is incorporated is travelling at high speed, the air flow acting on the wiper blade sets up a force which tends to lift the blade; and in extreme conditions this force can cause the blade to separate from the surface being swept, thus impairing the quality of the wiping action on the swept surface.
It has been proposed, in particular in the specification of French published patent application No. FR 2 513 952A, to provide air deflectors which are arranged parallel and at a suitable spacing from the wiping strip, the said deflectors including, or being arranged to extend from, a resilient bar which is carried by the wiping strip, in such a way as to divert the air flow away from the working zone of the wiping strip.
Although this deflector arrangement does partly overcome the problem of air flow setting up a lifting force, it does still reduce the quality of the wiping action performed by the wiping strip. What happens is that the deflector and the resilient bar tend to cause the wiping strip to become more rigid, and, in the case of a swept surface having a large curvature, for example windshields of automotive vehicles, the wiping strip is unable to hug this curvature accurately. The result is that during operation on certain parts of the windshield, its surface is not wiped, with the inevitable result that the driver's visibility is impaired.
In addition, this type of air deflector can, in the case in which the air flow penetrates between the wiping strip and the deflector, cause separation of the whole wiper blade, due to the creation of a lifting force on the face of the deflector which lies facing that of the wiping strip.